It's really not about that, Baggs. It's that people take time to respond (taking into account the development of the thread, noting what has been added to the OP) and then the next replies take no account of that whatsoever, and just respond to the OP, which will often not have all the information in it.
Subsequent replies do the same, and nothing makes any progress. What's the point of someone asking advice if the thread is going to go round and round because people can't be bothered to read the posts and see what has already been suggested but wouldn't work for whatever reason?
People will obviously agree with previous posts at times, and want to say so, but that's not the same thing at all. 'I agree with X - I did that and it worked really well' or whatever is adding something to the thread. It is agreeing with a suggesting that has already been discounted that is a bit pointless. It might have seemed a good idea, but if the OP has already said that it's not feasible in the circumstances, there is nothing to be gained by lots of posts suggesting it over and over, particularly when the thread has moved on since it as first mooted.